@Claireamydemi 

Hi,
What's your camera's model number, firmware, and hardware version? You can find them in the Tapo app > camera's Device Settings > Device Info page.

Do you mean you can't view your camera's live feed in the Tapo app when the phone uses mobile data, but you can view it when the phone is connected to a Wi-Fi network?
Please double-check whether the reported phenomenon has been resolved now.

If not, please check the LED status on the camera, such as solid green or solid red.

Best Regards